Substrate for mounting filaments in close-spaced parallel array

ABSTRACT

A substrate for mounting filaments in close, accurately spaced, parallel array. A soft wire is carefully wound upon a mandrel with successive turns tightly packed against each other. Replicas of plastic or other materials are made of the surface formed by the wire. The filaments to be supported are laid in the grooves in the replicas.

United States Patent [72] Inventor Harry J. Green, Jr.

Rochester, N.Y.

[21] Appl. No. 872,429

[22] Filed Oct. 29, 1969 [45] Patented June 8, 1971 [73] AssigneeNemonic Data Systems, Inc.

Denver, Colo.

Continuation of application Ser. No. 625,771, Mar. 24, 1967, nowabandoned.

[54] SUBSTRATE FOR MOUNTING FILAMENTS 1N CLOSE-SPACED PARALLEL ARRAY 1Claim, 7 Drawing Figs.

[52] U.S.Cl. 174/1, 161/123, 249/175, 264/220, 264/227, 340]?74 [51]Int. Cl. Gllc 5/04,

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Primary Examiner-Laramie E. Askin Attorney-Hoffman Stone ABSTRACT: Asubstrate for mounting filaments in close, accurately spaced, parallelarray. A soft wire is carefully wound upon a mandrel with successiveturns tightly packed against each other. Replicas of plastic or othermaterials are made of the surface formed by the wire. The filaments tobe supported are laid in the grooves in the replicas.

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,QBYWSIAM ATTORNEY SUBSTRATE FOR MOUNTING FILAMENTS IN CLOSE- SPACEDPARALLEL ARRAY BRIEF SUMMARY OF THE INVENTION This application is acontinuation of the U.S. Pat. application Ser. No. 625,771, filed onMar. 24, 1967 for Harry J. Green, Jr. entitled, Substrate For MountingFilament In Close-Spaced Parallel Array," now abandoned.

There has been much recent interest in thin film magnetic memory devicesof the type including filaments such as wires coated with thin films ofmagnetic material, typically applied by electrolysis or evaporation invacuuo. The filaments are typically about 0.004 to 0.005 inch indiameter, and the thin film magnetic materiai is typically about 1micron thick. The output signals produced in the operation of devices ofthis type are relatively small, typically on the order of a fewmillivolts, and it is important to achieve a high degree of uniformityin the spacings between successive wires when they are arranged inparallel array to form a matrix, otherwise variations in couplingbetween adjacent wires at different points along their lengths may tendto introduce errors into the system. Also, to minimize certaindeleterious effects due to magnetostriction, it is desirable to providefirm support for the wires that carry the thin film magnetic material.Finally in the interest of space conservation, it is desirable to spacethe wires as closely together as possible.

Briefly, a substrate in accordance with the invention comprises areplica of the surface formed by winding a soft metal wire upon a fiatmandrel with each successive reach of the wire straightened bystretching and carefully forced against the preceding reach. A mastermold is made from the mandrel, and the substrates are cast in the mastermold. Alternatively, more complex replication techniques may be usedsuch as, for example, techniques applied in the production of phonographrecords and of optical diffration gratings. As many of the replicas asdesired may be secured together to form'a relatively large substrate.Typically, the replica is made of an insulating material such as athermosetting resin, and an electrically conductive plate may be moldedinto the replica to provide an electrical ground plane.

DETAILED DESCRIPTION A presently preferred embodiment of the inventionwill now be described in detail in connection with the accompanyingdrawing, wherein:

FIG. 1 is a fragmentary isometric view of a mandrel partly wound withwire, indicating an initial step in the manufacture of a substrateaccording to the invention;

FIG. 2 is a cross section taken along the line 2-2 of FIG. 1;

FIG. 3 is a cross-sectional view of a mold according to the invention,illustrating casting of a substrate;

FIG. 4 is a partly schematic diagram in isometric form of the assemblyof individual units according to the invention to form a relativelylarge substrate;

FIG. 5 is a perspective view on a larger scale than FIG. 4 of a supportaccording to the invention;

FIG. 6 is a cross-sectional view of a support generally similar to theone shown in FIG. 5, but without a conductive ground plane; and

FIG. 7 is a cross-sectional view of the support shown in FIG.

form of a replica of a master mold 12, which is made by winding a softwire 14 upon a mandrel 16, the significant surface 18 of which has beencarefully finished to a high degree of flatness. To insure that the wire14 lies flat upon the mandrel, the edges of the mandrel around which thewire is turned are rounded over a relatively long radius such that thewire will readily accept the curvature. The wire 14, which may be, forexample, of copper, is straightened by stretching either just prior towinding or as it is wound. The winding is carefully done, and each turnof the wire is forced againstthe recedin one so that it lies "I abuttingengagement with it. A ter WIII ing, the mandrel with the wire 14 upon itis carefully inspected to insure that the wires are straight and true,free of foreign matter, and lie flat upon the mandrel. If desired, themandrel may be first. coated with a film of an adhesive material tosecure the wire 14 firmly upon it. Molds 20 are then made by castingupon the mandrel. The molds 20 may be made of any desired castingmaterial such as certain silicone compositions, many of which have beenspecially developed for use in dentistry, and which are capable offorming accurate negative images of the surface formed by the wire 14.

The molds 20 are then used to produce replicas 10 of the original mastermold 12. The replicas 10 are typically cast of an insulatingthermosetting resin selected from among those having good dimensionalstability. For certain uses, it is desired to provide a sheet ofconductive material, called a ground plane, closely adjacent to, butinsulated from, the wires of the magnetic memory. For this purpose,after the mold 20 is partly filled with the insulating material that isused to form the replica 10, a sheet 22 of conductive material is placedin the mold and pushed down until it comes into contact with and restson the lands 24 of the mold. The balance of the mold is then filled withthe insulating casting material, which is then hardened to form a rigidsubstrate for the wires of the magnetic memory or any other filaments.

The replicas I0 can readily be made with a high degree of accuracy, thatis, with very small deviations from the shapes and dimensions of thesurface of the wire 14 on the mandrel. For all practical purposes, thereplicas are exact copies of the surface. If reasonable care isexercised in winding the wire 14 upon the mandrel 12, a large number ofindividual replicas 10 may readily be arrayed in uniform registration toform an overall memory plane of any desired size. Each replica 10 isidentical to the next one, and alignment and registration problems are,therefore, minimized.

Another advantage in the practice of the invention relates to thecross-sectional shape of the grooves. The grooves are generally V-shapedin cross section so that the wires, or other filaments laid in them areurged toward and held in centered alignment with the grooves with a highdegree of uniformity and precision.

Iclaim:

l. A striated support for electrically conductive filaments or the likecomprising a body of stiff insulating material having a striated surfaceof similar shape to a surface formed by laying down successive lengthsof a round wire in straight abutting relationship upon a flat supportand a sheet of a conductive material molded integrally within said bodylying immediately beneath and substantially coextensive with thestriations to constitute a ground plane.

1. A striated support for electrically conductive filaments or the likecomprising a body of stiff insulating material having a striated surfaceof similar shape to a surface formed by laying down successive lengthsof a round wire in straight abutting relationship upon a flat support,and a sheet of a conductive material molded integrally within said bodylying immediately beneath and substantially coextensive with thestriations to constitute a ground plane.